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Evaluation of ground-motion characteristics for seismic hazard prediction

地震灾害预测中的地面运动特征评估

基本信息

批准号：
07555140
负责人：
OHMACHI Tatsuo
金额：
$ 4.61万
依托单位：
TOKYO INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

项目摘要

Strong-motion and microtremor observations are carried out in Kamakura and Kitahassaku area, Yokohama, in order to evaluate ground-motion characteristics in the areas. In Kamakura, four accelerographs are installed on soft rocks and Holocene lowland. The observed records contain siteamplification characteristics at each site although the records are contaminated by building vibrations. It is shown that the site-amplification characteristics can be detected by H/V spectral ratios of microtremors. The H/V spectral method is modified by introducing coherence between horizontal and vertical motions. The new method is applied to site-amplification evaluation in Kamakura. The results are consistent with the damage distribution in Kamakura area during the 1923 Kanto earthquake. In Kitahassaku area, three accelerographs are installed on loam plateau and Holocene lowland. Strong-motion observation shows that a plateau site has larger site-amplification characteristics in comparison to lowland sites by a factor of about 1.5 in peak horizontal ground velocity and about 2 in spectral peak amplitudes of Fourier amplitude-spectra. The amplification is due to subsurface soils which are accumulated on soft rocks. The site-amplification characteristics at the strong-motion sites can be detected by H/V spectral ratios of microtremors. Spot microtremor observations conducted in the area demonstrate that resonance periods on plateaus are related to elevation ; high site amplification areas distribute along rivers in the lowlands and the Shimosueyoshi plateau. The comparisons of spectral characteristics of strong motions and microtremors show the applicability of microtremors to evaluation of ground-motion characteristics for seismic hazard prediction.

为了评价横滨市镰仓和北八作地区的地震动特征，进行了强震动和微动观测。在镰仓，四个加速度计安装在软岩和全新世低地上。观测到的记录包含siteamplification特性在每个站点，虽然记录被污染的建筑振动。结果表明，场地放大特征可以通过地脉动的H/V谱比来检测。通过引入水平运动和垂直运动之间的相干性，对H/V谱方法进行了改进。新的方法被应用到站点扩增评价在镰仓。这一结果与1923年关东大地震时镰仓地区的震害分布相一致。在北八作地区，在壤土高原和全新世低地上安装了三个加速度计。强震动观测表明，高原场地具有比低地场地更大的场地放大特性，其水平地速度峰值约为1.5倍，傅立叶振幅谱的谱峰值振幅约为2倍。放大是由于地下土壤积累在软岩。强震场地的场地放大特征可以通过地震动的H/V谱比来检测。在该地区进行的现场微动观测表明，高原上的共振周期与海拔高度有关，高场地放大区分布在沿着的低地和下末吉高原。通过对强震和地震动频谱特征的比较，说明了地震动在地震危险性预测中对地震动特性评价的适用性。